This book focuses on the cosmological implications of the gauge theories of particle physics and of string theory. It first examines relics of early phase transitions, more generic relics baryons, neutrinos, axions, and supersymmetric particles neutralinos and gravitinos. The author next studies supersymmetric theory, supergravity theory, and the constraints on the underlying field theory of the universes inflationary era. The book concludes with a discussion of black hole solutions of the supergravity theory that approximates string theory at low energies and the insight that string theory affords into the microscopic origin of the